In certain high-voltage propelled vehicles such as hybrid-electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), and electric vehicles (EV), a relatively high-voltage (HV) power supply, e.g., a battery or other electrochemical energy storage device, provides a source of at least a portion of the required propulsive power. If so equipped, an engine may be selectively powered off when the vehicle is idling or at a standstill in order to conserve fuel, and/or the vehicle can run entirely on electrical power provided by the HV power supply depending on the vehicle design.
The HV power supply can store energy at a relatively high voltage, typically on the order of 60 volts up to 300 volts or more, in order to provide sufficient electrical power for propelling the vehicle, as well as to energize various HV components and systems aboard the vehicle. Common HV vehicle components and systems may include one or more electric motor/generator units (MGU), a traction power inverter (TPIM), an air conditioning compressor inverter module (ACCM), and/or an auxiliary power module (APM).
The HV power supply can transmit HV electrical current across positively and negatively charged conductive rails of an HV direct-current (DC) bus portion of a dedicated HV electrical circuit. The HV DC bus may be shared by multiple power electronic converter devices, e.g., the TPIM and ACCM noted above. Each of these power electronic converter devices may include DC-side filter components, such as internal capacitors and/or inductors, in order to meet the various circuit requirements, e.g., those related to ripple voltages and currents. The DC-side filter components may also contain electromagnetic-compatible (EMC) components, for example common-mode choke components or additional capacitors. In addition, the DC cables connecting the power electronic converters have equivalent series inductances that may add to those of the DC-side filter components.
The inductors and capacitors form a circuit having an electrical resonance frequency, i.e., a particular high-magnitude alternating current (AC) that oscillates in the circuit when an equivalent series impedance between a circuit input and output is at a minimum. If any power electronic converter within the HV system generates frequency components on the shared DC bus that fall within the resonance frequency range, the DC bus will be excited, and an electrical resonance will result. In some DC bus control algorithms, a pulse-width modulation (PWM) switching frequency profile may be caused to vary with motor speed and torque. For example, the PWM switching frequency may decrease with an increasing torque for a given motor speed, and may increase with increasing speed for a given motor torque.